This invention relates to the diffusion of ultraviolet light and relates in particular to a method of contructing a near-Lambertian diffuser for transmittance and reflectance of ultraviolet light. A Lambertian diffuser is one which diffuses a point (concentrated beam) source of reflected or transmitted light in a cosine law or circular pattern.
Lambertian diffusers are useful in calibrating instrumentation in the laboratory and for use in optical equipment. The subject invention was first used in the calibration of an optical radiometer.
Although opal glass serves as a near-Lambertian diffuser of visible light, no comparable prior art diffuser has been developed for use in the 2000-4000 A ultraviolet range. Absorption in the diffusing layer or scattering out the edge of the diffuser causes the diffusion pattern to deviate from Lambertian. When a thinner diffusing layer is used in an attempt to avoid absorption, a large specular or unscattered component of the ultraviolet light develops causing deviation from Lambertian.